On a hot summer day, tired by long discussions, three wise sages were slumbering inthe shade of a tree. A prankster was walking by, and couldn't pass up such an opportunity. He took a piece of charcoal, and put a black spot in the middle of each sage's forhead, careful not to wake them.

When the men did wake, they looked at each other, saw the black marks and began laughing. Each one thought that his two friends had the mark, while his own forhead was clean.

Suddenly, one of them stopped laughing, having realized that his forhead must be dirty as well. How did he arrive at this conclusion?

(In reply to this is the solution by theBal)

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the solution doesn't make sense because one person can have a clean face and still another can figure out his is dirty. If I'm C and I assume that my face is clean while seeing A & B both with dirty faces and both laughing - and also assuming that once somebody realizes that their face is dirty they will stop laughing - then I can assume that they are laughing at each other. But then to say that if my face is clean then one of the others would have stopped laughing because my clean face would tell them that theirs is dirty and since they are still laughing mine must be dirty too, is wrong! Because what would happen after that? one of the others would see that I stopped laughing and then think that their face could still be clean. (thinking that that's how I came to that conclusion) So seeing one of the others stop laughing doesn't necessarily mean that your face is clean so you can't say that because they are still laughing that your face must be dirty. hope that makes sense...

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Posted by Danny on 2004-04-14 16:42:23